Means for preventing condensation op moisture from flue gases



Oct. 3, 1933.

e. G. SCHMIDT MEANS FOR PREVENTING CONDENSATION OF MOISTURE FROM FLUE GASES 2 sheets-sheet 1 Filed Aug. 16

fad V013 M Affazjrzyz Del. 3, 1933. 5, DT ,928,822

MEANS FOR PREVENTING CONDENSATION OF MOISTURE FROM FLUE GASES Filed Aug. 16, 1930 2 Sheets-Sheet 2 Patented Oct. 3, 1933 UNITED STATES MEANS FOR PREVENTING CONDENSATION OF MOISTURE FROM FLUE GASES George G. Schmidt, Forest Hills, N. Y., assignor to Carrier Engineering Corporation, Newark,

Application August 16,

2 Claims.

This invention relates to means for preventing condensation of moisture from gases in flues, and more particularly to novel means for preventing condensation in the smoke flues of air heating furnaces of the sort disclosed in my application for patent, Serial No. 267,094, filed April 3, 1928 issued August 26, 1930 as Patent No. 1,773,870. 7

It is well known that there is considerable condensation of moisture from the water vapor in the products of combustion in the smoke flues, particularly of air heating furnaces, in which gaseous and other hydrocarbon fuels are burned. The condensate corrodes and soon destroys the metal of the flues and it is also injurious to the mortar and brick of chimneys. If the efliciency of the furnace is such that the exchange of heat from the burning gases to the air being heated is sufficient to cool the products of combustion to-or below their point of saturation, the resulting condensation from the products of combustion is a source of serious objection and trouble.

One object of my invention is to provide means of improved construction which will effectually prevent condensation from the products of combustion or flue gases in flues, particularly the smoke flues of furnaces.

Other objects of the invention are to provide means whereby heated air, or other suitable gaseous medium, is discharged into the flue so as to produce a stratum or layer of gaseous medium within the flue between the wallsof the same and the products of combustion and thereby prevent the chilling of the products of combustion by contact with the walls of the flue and the deposit of condensation on the walls of the flue; and also to provide means for preventing condensation of moisture in flues which have the features of advantage and improvement hereinafter described and set forth in the claims.

The accompanying drawings illustrate means of practical construction embodying my invention applied to the smoke flue of an air heating furnace for preventing condensation from the products of combustion in said flue.

Fig. 1 is a fragmentary. sectional elevation of the furnace and smoke flue.

Fig. 2 is a sectional plan view of the smoke flue on an enlarged scale on line 2-2, Fig. 1.

Fig. 3 is an enlarged, sectional elevation of the smoke flue on line 33, Fig. 2.

Fig. 4 is a plan view of the condensation-preventing device on a smaller scale.

10 represents the casing of an air heating furnace, 11 the air heating unit or heat interchanger 1930. Serial No. 475,733

thereof, and 12 the smoke flueor flue through which the products of combustion discharge from the furnace.

The furnace may be of the construction more fully described in said application, or of other construction. As fully explained in said application, the products of combustion flow through suitable passages in the heat interchanger and pass therefrom into the discharge or smoke flue 12, and the air to be heated passes in contact with and through suitable passages in the heat interchanger in heat exchange relation to the hot gases of combustion, and is adapted to discharge from the furnace through one or more hot .air pipes or conduits 13.

The smoke flue shown comprises a lower section 12 which communicates with the gas passages of the heat interchanger 11, an upper section or smoke pipe 14, and a downwardly flaring, intermediate section 15 to which the upper section 14 is connected, and the lower end of which surrounds and is spaced from the upper end of the lower section 12 to form the usual back draft diverter opening 16 between the lower end of the section 15 and the lower section 12. 17 represents the usual double conical deflector supported centrally within the smoke flue above the upper end of the lower section 12 for deflecting the flue gases, in case of a back draft, away from the upper end of the lower section 12 and out through the back draft diverter opening 16. As shown, this deflector is supported by radial plates 17a secured to and extending inwardly from the intermediate section 15.

18 represents a pipe or passage through which a suitable gaseous medium, preferably air heated by the furnace, is adapted to be discharged into the smoke flue for preventing condensation in the flue. As shown, this pipe has an open inlet, or lower end arranged within the furnace casing adjacent to the upper portion of the air heating unit 11 so that the air heated by the furnace will enter and pass through the passage 18. At its opposite end, this passage has an outlet constructed so as to discharge the heated air into the smoke flue in an annular or hollow layer or stream in contact with or adjacent the inner surface of the walls of the flue so that the heated air will envelope the products of combustion in the flue and tend to pass up the flue against or close to the inner surface of the flue and between the same and the products of combustion. Preferably an annular shell 19 surrounds and is secured to the intermediate section 15 of the flue,

with its contracted upper end separated by an 11 annular space 22 from the contracted upper end of the intermediate section 15 of the flue. The upper section 14 of the flue fits down over the upper end of the shell 19; The bottom of the shell 19 is closed by a wall 20, so that the shell forms an annular chamber 21 surrounding the intermediate section 15 of the flue and having an annular outlet formed by the space'22 through which the heated air admitted to the chamber 21 can discharge in an annular column into the upper section 14 of the smoke flue. The upper ends of the shell 19 and the flue section 15 are held in concentric spaced relation by suitable spacers 23. The passage 18 preferably connects tangentially with the chamber 21, as indicated in Figs. 2 and 4, so that the heated air from the furnace will enter and fill the chamber 21 and will discharge therefrom through the annular outlet 22 in an annular or hollow layer completely encircling the interior of the upper section of the smoke flue.

The furnace is preferably equipped with the usual fan or means for creating a forced draft of the air through the furnace, and the pressure in the furnace thus created insures the proper flow of the air through the passage 18 and annular chamber 21, and the discharge of the same through the annular outlet 22 into the smoke flue.

Since the air which is discharged into the smoke flue has been heated in the furnace, it is relatively hot and dry and has a low dew point or low relative humidity. Therefore, the introduction of the air into the smoke flue not only increases the temperature of the gases in the flue, thereby reducing the relative humidity thereof and. increasing the moisture-carrying capacity of the flue gases, but the introduction of the air annularly into the flue in contact with or adjacent the walls of the flue, or between the same and the products of combustion, as explained, tends to envelope the products of combustion in a relatively hotter layer of air which prevents the products of combustion from being chilled by contact with the walls of the flue, which otherwise would be of lower temperature by reason of the lower temperature of the air externally surrounding the flue. It will also be noted that the heated furnace air is also introduced into the flue between the walls thereof and the outside air that is drawn into the flue through the diverter opening 16. This further aids in keeping the walls of the flue warm enough to prevent precipitation of moisture thereon. The condensation of moisture from the gases in the flue and the deposit thereof on the walls of the flue are therefore effectually prevented.

I claim as my invention:

1. The combination with an air heating furnace, and a flue for the discharge of the products of combustion from the furnace, of means constructed to discharge air heated by said furnace into said flue in proximity to the inner surface of the walls of the flue and between the same and the products of combustion in the flue.

2. The combination with a furnace, and a flue for the discharge of products of combustion therefrom, said flue having a back draft diverter opening through which air can enter the flue, and means constructed to discharge a relatively warmer gaseous medium annularly into said flue between the walls thereof and the column of air entering through said diverter opening.

GEORGE G. SCHMIDT. 

